The present invention relates to a cycloolefin-based polymer with a very low content of foreign matters and to a molded article obtained by using the cycloolefin-based polymer. The invention also relates to a process for producing a cycloolefin-based polymer with a very low content of foreign matters.
An integrated circuit (IC) is an electronic circuit provided with a large number of transistors, resistances, capacitors, etc. on the surface of a silicon wafer several millimeters square. With recent increasing requirement for electronic instruments of more enhanced performance and smaller size, the degree of integration of the IC is becoming increasingly high, and the IC is developing through LSI to super LSI and VLSI (ultra LSI). In the LSI and super LSI, the necessary circuits are formed by printing the circuits on a silicon wafer by using a photosensitive resist or the like, and then successively applying the treatments of surface oxidation, etching by chemicals, doping, vapor deposition, supersonic cleaning, etc. With the increasingly high degree of integration of the IC, the width of the circuit is decreasing to as small as the order of submicron. Consequently, when impurities, particularly minute particles, are present on the silicon wafer surface, they will adversely influence on the withstand voltage characteristic of the oxide film of the LSI, and the extent of the influence is increasingly large as the degree of integration increases. Therefore, for example, an ultrapure water having a very low content of minute particulate foreign matters is used in the cleaning step.
However, the etching treatment with chemicals and the cleaning with ultrapure water, which are commonly conducted by placing the silicon wafer in a plastic case called a carrier and immersing it in an etching liquid or ultrapure water, have a problem in that minute particulate matters are generated from the carrier itself. Thus, these plastic cases have hitherto been made by using fluoresins, such as PFA, polypro-pylene or like resins, which are excellent in chemical resistance, but these resins have shortcomings in that they are apt to generate minute particulate foreign matters on contacting with the silicon wafer owing to their low surface hardness and that they do not give satisfactory dimensional accuracy and surface smoothness at the time of molding.
As a means for solving such problems, JP-A-7-126434 discloses a treating vessel for use in semiconductor production steps which uses a thermoplastic norbornene type resin. However, the vessel also shows the generation of minute particulate foreign matters at the time of ultrasonic cleaning, etc. and hence cannot be deemed fully satisfactory.